Use `fixedOverflowWidgets` for playground popover (#8458)
After some Googling...
<img width="656" alt="Screen Shot 2023-11-03 at 12 23 09 AM"
src="https://github.com/astral-sh/ruff/assets/1309177/be6aaa3d-0068-4bad-a27f-01785179567d">
Closes https://github.com/astral-sh/ruff/issues/8442.
